1. Field of the Invention
The present invention relates to a battery pack with which it is possible to enhance impact resistance performance.
2. Description of the Related Art
A battery pack includes a plurality of cylindrical battery cells arranged in a plurality of rows and a plurality of layers, a partition member for partitioning the battery cells from each other, electrode tables for electrical connection between terminals of the battery cells partitioned by the partition member, a lower case for containing the battery cells electrically connected through the electrode tabs, and an upper cover for covering the lower case in which the battery cells are contained, and is detachably attached to a body of an electronic apparatus, to be used as a power source for the electronic apparatus (refer to Japanese Patent Laid-Open No. 2003-257388).
In battery packs according to the related art, the material thicknesses of the lower case and the upper cover are set at minimum thicknesses conforming to the UL (Underwriters Laboratories Inc.) 94 Standard, for promising a reduced size instead of a larger outer size. Therefore, in the battery packs according to the related art, the material thickness of the partition member is set to be larger than that of the casing, and enhancement of the impact resistance of the partition member for partitioning the battery cells contained in the casing is contrived, so as to enhance the overall impact resistance performance.
Here, the battery packs for use in business-use electronic apparatuses need to have a rated voltage of about 14.4 V, as contrasted to a rated voltage of about 7.2 V which is requisite for battery packs for use in private-use electronic apparatuses.
Therefore, in the case of the battery cell composed, for example, of a cylindrical lithium ion secondary cell, the rated voltage of one battery cell is about 3.6 V, so that it suffices to connect two battery cells in series in order to assemble a battery pack for use in private-use electronic apparatuses needing the rated voltage of about 7.2 V. On the other hand, in order to assemble a battery pack for use in business-use electronic apparatuses needing the rated voltage of about 14.4 V, four battery cells have to be connected in series. Thus, as compared with the battery pack for business-use electronic apparatuses, the battery pack for business-use electronic apparatuses is larger in the number of battery cells, is heavier in weight, and is accompanied by a stronger need for strength of the casing itself which is exposed to the exterior.